Method of making lawn mower handles



Patented Mar. 9, 1943 METHOD oF MARIN HAND Truman B. Funk, Jackson, Mich., assignor to Yard-Man, Inc., Jackson, Mich., a corporation of Michigan G LAWN MOWER LES Application May 2, 1940, Serial No. 332,902 3 Claims. (Cl. 153-79) The present invention relates to a method of forming lawn mower handles and the like and more particularly to a method of internally expanding an end portion of a tapered sheet metal tube employable for lawn mower handles and the like.

The method comprising the present invention relates to a step in the making of a lawn mower handle or the like disclosed fully in my co-pending application executed and filed on an even date herewith. It has been discovered that handles of the character described constructed from tapered sheet metal tubes have certain advantages over the conventional wood handles. In constructing a handle of the character described from a tapered tubular sheet metal member, an end portion of substantially rectangular crosssection and of substantially uniform width and depth throughout its length is provided to which the lawn mower connecting forks are clamped. While it might be considered at first blush that in order to form such a rectangular endv section on a tapered tube, there would be required merely a rectangular punch to be forced into the end of the tube, it has been found that a rectangular punch when forced into the end of a light gauge tapered tubular sheet metal member to form the same in a single operation will cause the same to wrinkle. According to the present invention, wrinkling is eliminated by bulging out the opposite sides of the punch corresponding to those sides of the tube having relatively greater width. This form of a punch provides the expanded end portion of the tube with bellied side portions which have greater resistance to the axial thrust of the punch and therefore do not wrinkle.

An object of the invention is to provide a method for expanding an end portion of a tapered sheet metal tube into a portion of substantially uniform width and depth without Wrinkling the same.

Another object of the invention is to provide a method of expanding an end portion of a tapered sheet metal tube into a portion of substantially uniform width and depth which comprises inserting into the end of the tube a punch of substantially rectangular cross-section having the relatively wider sides thereof bulged outwardly.

'I'hese and other objects will be apparent from the following specification when taken with the accompanying drawing, in which:

Fig. 1 is a partial elevation of a handle, according to the present invention, showing its normal association with forks for connecting the same to a lawn mower,

Fig. 2 is an elevation of a portion of a tapered tubular blank and an expanding punch, according to the present invention, about to be inserted thereinto, Y

Fig. 3 is a sectionon the line III- III of Fig. 2,

Fig. 4 is a section of the expanding punch on the line IV-IV of Fig. 2,

Fig. 5 is a section on the line V-V of Fig.l 2,

Fig. 6 is an elevation of a tapered tubular member expanded, according to the present invention,

Fig. 7 is a sectionon the line VII-VII of Fig. 6,

Fig. 8 is a cross-section corresponding to Fig. 4 of an alternative form of expanding punch, and

Fig. 9 is a cross-section corresponding to Fig. '7 of an alternative form of the handle attachment portion.

Referring particularly to the drawing, the reference character I indicates a portion of a handle, according to the present invention, which is tapered and constructed of sheet metal. As shown particularly in Fig. 3, disclosing a section of the tubular member I, the tubular member I is elliptical in cross-section adjacent the larger end thereof. In its finished form, the larger end of the tube I is expanded into a portion 2 of substantially rectangular cross-section and substan- K tially uniform width and depth, against which fork members 3 connected to a lawn mower or the like, not shown, are clamped by bolts 4.

According to the present invention, the expanded end portion 2 of the handle I is formed by forcing a punch 5, shown in Fig. 2, into the larger end of the tubular member I. The punch 5, shown also in section in Figs. 4 and 5, is substantially of rectangular cross-section and substantially uniform in width and depth throughout its length, except for an entering nose portion 6, which is more or less elliptical in crosssection to conform to the cross-section of the end of the tubular member I for the purpose of guiding the punch 5 thereinto.

It has been found that when the punch 5 is of true rectangular cross-section that the Wider sides of the end portion 2 wrinkle as the punch is pushed into the end of the member I due to the resistance created in the expanding action and the frictional resistance of the punch 5 against the wider sides. According to the present invention, this wrinkling is eliminated by providing the wider sides of the punch 5 with bulges 1.

When the punch 5 with the bulges 'I is forced into the end of the tubular member l, the end portion 2 of the tubular member l is provided with bulges 8, shown particularly in Fig. '7. The bulges 8 generally follow the contour of the bulges 1. The bulges 8 have the effect of constituting the wider sides of the portion 2 more rigid than they would be if flat, with the result that they are able to withstand the inward moving and expanding action of the punch 5 without wrinkling.

In Fig. 6 is shown the end portion 2 of the tubular member I in full line and the original position of the expanded end portion of the tubular member I in dotted line. It will be observed from Fig. 6 that the tubular member l is shortened by the expanding of the end portion 2 and also that the narrower side portions are shortened more than the wider side portions with the result that the end 9 of the portion 2 is arcuate, as shown in Fig. 6.

While the bulges 1 in the punch 5 are disclosed in one particular shape, it will be apparent from the foregoing description that no particular shape is necessary, other than to provide the end portion 2 with bulges 8 which will make the wider sides of the end portion 2 sufciently rigid to withstand wrinkling under the inward expanding movement of the punch 5. For example the bulges 1 of the punch 5 could be replaced by generally curved side contours I8 indicated in Fig. 8 which is a cross-sectional view, corresponding to Fig. 4, of an alternative form of punch 5.

As an embodiment of the invention it is contemplated that the end attachment portion 2 of the handle may be subjected to an optional, additional forming operation after that provided by the punch 5, to provide the end portion 2 with a rectangular cross-sectional form Il, as shown in Fig. 9. This form could be provided with a punch, not shown, of a cross-sectional form corresponding to the form ll.

Further embodiments of and modifications to the foregoing invention will be clear to those skilled in the art to which the invention pertains. It is to be understand, for instance, that the nose 6 of the punch 5 may take any form that may be desired as the shape of the nose G is not a limiting feature of the invention.

resulting expanded portion has at least two oppo- Y site sides outwardly bulged, and forcing into said expanded portion a second punch having substantially straight sides and being of substantially rectangular cross-section to form said expanded portion into a portion having unbulged sides.

2,. The method of expanding anv end portion of a tapered sheet metal tube to a portion of substantially parallelogrammatic cross-sectional configuration, and of substantially uniform Width and depththroughout its length, which comprises forcing into said end portion a punch so shaped that as it passes thereinto it will expand said end portion to the said configuration and simultaneously bulge outwardly at least two opposite sides of said end portion to increase their resistence to wrinkling under the action of the punch.

3. The method of expanding an end portion of a tapered sheet metal tube of substantially elliptical cross-section to a portion of substantially rectangular cross-.section and of substantially uniform width and depth throughout its length, the relatively short parallel sides of the expanded portion being planar, which comprises forcing into said end portion a punch so shaped that as it passes thereinto it will expand said end portion to said cross-section, and will simultaneously bulge slightly outwardly the relatively long sides of said end portion to increase their resistance to wrinkling under the action of the punch.

TRUMAN B. FUNK. 

